It is proposed to undertake a co-ordinated group study of iron transport by the intestinal mucosal cell. The work is designed to interface with a larger research program involving studies of food iron availability in man and studies of iron absorption and iron balance in various clinical disorders. Various phases or iron transport by the mucosal cell will be isolated for separate study. Initial uptake of luminal iron will be examined by a model employing suspensions of isolated mucosal cells. Studies of intracellular iron transport in these isolated cells will employ a battery recently developed radioimmunometric assays for direct measurement of proteins inolved in iron transport and storage within the mucosal cell. Studies of iron release and internal regulation of muscosal cell transport will initially attempt to identify an animal species other than rat which more closely resembles man in respect to iron assimilation. It is believed that the methods developed in this program will be directly applicable to the study of human iron absorption and its disorders.